I've been playing too much Mass Effect lately, and I got to thinking: "How would the internet work in space colonies, sans FTL communications?"

For colonies in orbit or on the Moon, latency would be a matter of seconds. Traditional HTTP protocol would still work, albeit slowly. I imagine most users would use an Earth-based proxy server that would fetch pages on their behalf and then compress the HTML and associated media into a single archive, thereby reducing the number of round-trips needed to load a page to just one or two.

For colonies on Mars or further out in space, latency would be measured in minutes. Nobody is going to want to wait that long for an HTTP connection to open, so a second, local caching proxy would be needed. Requests for static pages would be served from the local cache, which would receive regular push updates from earth. Dynamic content would be retrieved in much the same way as described in the previous scenario, though the extreme latencies involved would eventually force major content providers to setup localized mirrors.

Further out in space, latency would be measured in hours or even days (if humanity ever ventures beyond our solar system, communications could indeed take years). All traditional internet protocols would be utterly useless at this point, which is where Freenet comes in. Each town would have a powerful server node with many Terabytes of storage containing highly compressed copies of the most popular pages. When a page is requested, the node would follow standard Freenet protocol to retrieve it, and then store it locally for future reference. The pages would then be re-retrieved and the local copies updated regularly.

Have you heard of the Interplanetary Internet? It's how NASA is solving that exact problem, with a lot of backing from Google as well. It's based around delay-tolerant networking protocols, and is being designed by Vint Cerf (amongst others), one of the original co-designers of TCP/IP.

I actually thought of the NASA protocol right away, but apparently I wasn't alone.

Actual inter-planetary internet would likely be near to impossible, to say nothing of extra-solar... I think you nailed it with the title: it would pretty much have to be built like freenet, distributed storage, at least for the off-planet stuff, refreshed periodically, more often for the more popular, less for the fringe stuff.

Direct communications would likely be limited to emails, or thier video counterparts. I can't see real-time conversations working too well between say, mars and pluto, even at closest approach. Might be used for stuff that needs an answer NOW.